Objective comprising three lens members axially air separated from each other in optical alignment



350-476 I SEARCH ROOM Dec. 8, 1953 BERTELE 2,661,660 OBJECTIVE COMPRISING THREE LENS MEMBERS AXIALLY AIR SEPARATED FROM EACH OTHER IN OPTICALALIGNMENT Filed Jan. 19, 1952 Film -//7venfor.-

Patented Dec. 8, 1953 UNITED STATES OBJECTIVE COMPRISING THREE LENS MEMBERS AXIALLY AIR SEPARATED FROM EACH OTHER IN OPTICAL ALIGNMENT Ludwig Bertele, Heerbrugg, Switzerland Application January 19, 1952, Serial No. 267,271

1 Claim.

The present invention is relative to an objectiv substantially comprising three lens members axially separated from each other by air spaces of which two converging members include one member bent towards the object. The air space separating the first member from the second one has the shape of a diverging lens bent towards the object, and the air space separating the second member from the third member has the form of a converging lens with its minor bent surface directed towards the image. The first member generally is a single converging lens. The second member consists of single lenses being either cemented together or separated by small air spaces, the one of said lenses having a diverging power. The third converging lens member has a cemented surface strongly bent towards the image with a refractive index being greater at the concave side of this surface than at the convex side. With this cemented surface the problem of diminishing the spherical zonal image errors and of eliminating the chromatic image errors to be solved.

Known objectives of this kind result with an aperture ratio of 1:2 in an effective image angle of :15. Beyond this limit there already arise chromatic image errors. Investigations aiming to further amplify the image angle with this sequence of lenses proved it to be more advantageous according to the present invention to satisfy the following three conditions simultaneously: firstly to choose the axial thickness of the second lens. component member between 0.12-f and 0.26-f, i being the total focal length of the objective, secondly to choose the values of 111; v1 and n2; 1;: so that the product of (121-1) (nz-1) (v1+v2) is greater than 45.0 and smaller than 60.0, and thirdly to choose the number of refractive index for the d-line as regards the negative lens of the second member less than 1.680. With this it is possible to reduce the axial thickness of the second member or to diminish the meniscus shaped deflection without detrimentally influencing the factor decisive for the image flattening whereby the conditions are embodied for amplifying the efiective image angle. I

Two examples of objectives according to the present invention with an aperture ratio of 1:2 and with an efiective image angle of 117.5 and of the focal length of 100 mm. are given in the following.

The drawing shows a section taken along the axis of an objective embodying this invention, which drawing serves for illustrating both said examples.

L1 is the lens representing the first member.

L2. L and L4 are lenses cemented together which constitute the second member.

L5, L6 and In are likewise cemented togethe and constitute the third member.

In Example 1 the axial thickness of the second lens component is 0.184-f. The result of the product of (n1-1)-(n21)-(v1+vz) amounts to 47.8. The refractive index of the negative lens L4 of the second member amounts to 1.65044.

In Example 2'the axial thickness of the second lens component is 0.184-1. The result of the product of (n11')-(n21)-(v1+vz) amounts to 48.1. The refract1ve 1ndex of the negative lens L4 of the second member amounts to 1.6364.

Example 1 r =+60.00 L, d1=6.67 1.64192 58.0

r2=+32o.o0

z,=0.33 T3=+31199 L2 d2=7.07 1.64192 58.0

n=+50.67 L5 a==ss0 1.46661 64.5

r5=6l3.34 L. d4=2.53 1.65044 34.6

lz=17.33 r =l200.00 L5 d5=a20 1.50137 56.5

rg=+54.00 L5 d4=12.03 1.65400 53.8

n=20.0l L1 d7=5.47 1.53240 56.1

L being the lenses, the respective indices defining the order of sequence;

r being the radii of the refracting surfaces, the respective indices likewise defining the order of sequence.

Example 2 L T1=+59.53 d 6 67 1 l =0.33 L fa=+32.20 d

1 2=7.07 1.64135 L n=+51.07 d 8 6 58 5 a 7 1.464 L T5= -453.33 (i 50 7 1 =2.67 1.63

z=17.a3 L T7= 1173.4 d

5 =3.33 1.51742 L rs=+52.67 d 5 52 2 5 =12.s0 1.65350 L ro= 19.98 53 4 1 =5.47 1.58100 L being the lenses, the respetcive indices defining the order of sequence;

1' being the radii of the refracting surfaces, the respective indices likewise defining the order of sequence.

3 I claim: Objective substantially comprising three lens component members axially separated from each other by air spaces of which the first said member directed towards the object is of convergent 5 power and has a refractive index n1 for the d-line and an Abbe Number in, the second said member is bent towards the object and composed of single lenses the first lens of which adjacent the said first member having a refractive index 10 m and an Abbe Number 02, and another lens of said second member being of divergent power, and

the third said member is of conyergent power and me udes two lenses cemented together, the

cemented surface being strongly bent towards 1 the image, the refractive index of the lens adjacent the concave side of said surface being higher than the index of the lens adjacent its convex side, the first air space being in the form of a diverging lens with its less curved surface directed 20 towards the object and the second air space being of the form of a converging lens with its less curved surface directed towards the image,

the axial thickness of the second said lens component member being chosen between 012-! and 0.26-f, i being the total focal length of the objective, the values of m; w and n2; 1): being chosen so that the product of (m-l) -(na-l) -(v1+vz) is greater than 45.0 and smaller than 60.0, and the number of refractive index for the d-line of said diverging lens of the second said lens component member being chosen smaller than 1.680.

LUDWIG BERTEIE.

References Cited in the file of this patent UNITED STATES PATENTS 

